1. Field
The following description relates to a method of controlling an automatic gain in a receiver and an automatic gain controlling apparatus using the same.
2. Discussion of Related Art
A radio signal in wireless communication system may get distorted by the environment condition in which the signal travels, and such distortion needs to be compensated properly to guarantee enough receiver performance. AGC (Automatic Gain Control) is a basic compensation function, which maintains a constant internal signal strength regardless of the antenna input power to minimize performance loss in data processing.
In WLAN (Wireless Local Area Network) communication, smaller environmental effect on signal characteristics is expected since a narrower space and lower moving speed of terminals are assumed there. But WLAN receivers generally need to be always ready to detect other terminals as well as AP to support a carrier sense multiple access (CSMA) based access operation, and the antenna input power may change in a random and abrupt manner from packet to packet. Therefore, AGC operation must be completed individually for each packet and faster AGC algorithm would be favorable in WLAN receivers. The conventional AGC algorithm includes a binary tree search AGC algorithm, and an RSSI based AGC algorithm.
In general, AGC involves a process of receiver gain change and ADC input power measurement. Since the signal fluctuation may be caused by receiver gain change, some transient interval before ADC power measurement may be needed and there is a limit in reducing an AGC operation period for stable power measurement. In addition, the receiver gain may increase or decrease during a convergence process of the general AGC operation, so there is a need of a hysteresis area to better ensure a stable convergence even with some measurement errors or external noise factors. This need of a hysteresis area is also a limiting factor in enlarging the receiver dynamic range.